Introduction. Chronic thromboembolic pulmonary hypertension (CTEPH) is a type of pulmonary hypertension characterized by obstruction of the pulmonary arteries by organized thrombi. Secondary hypoxia-mediated bronchoconstriction could be the cause of an obstructive ventilatory defect, while pulmonary infarction or right heart failure could be correlated with a restrictive ventilatory defect. Low diffusion capacity of the lungs for carbon monoxide (DLCO) level is the consequences of microvasculopathy.

Aim. The aim of the study was to investigate the pattern of lung function impairment in patients suffer from CTEPH.

Methods. The study was designed as a descriptive study. The study included patients with confirmed CTEPH without obstructive or restrictive lung diseases. Pulmonary function tests (PFTs) were performed and interpreted according to ATS/ERS guidelines from 2005. PFTs were performed in the stable phase of the disease.

Results. The study included 60 patients (mean age 76.13 ± 2.16 years, 60% female) over a three-year period, from January 2019 to December 2021. Obstructive ventilatory defect was registered in 4 patients, 6.66% (FEV1/FVC 67.82 ± 2.15), restrictive ventilatory defect in 17 patients, 28.33% (TLC 3.92 ± 0.54 l, 68.5 ± 2.21% pred.), mixed ventilatory defect was not registered. All patients had a reduced DLCO values (3.73 ± 1.28 mmol/min/kPa, 48.87 ± 15.32% pred.), where the Krogh's constant was 0.91 ± 0.23 mmol/min/kPa/l, 70.27 ± 16.32% pred.

Conclusions. The pattern of lung function impairment with restrictive ventilatory defect and reduced DLCO values indicates a differential diagnosis of CTEPH in patients without other lung diseases.